Device for sealing a projection exposure apparatus

ABSTRACT

A projection exposure apparatus is equipped with an illumination system, a reticle, a projection objective and an image plane. Interstitial spaces between the individual elements of the apparatus are open to the ambient space. A gas purge device which carries a stream of noble gas or nitrogen is arranged in at least one of the interstitial spaces. The gas purge device is of a shape and size so that one or more interstitial spaces are at least to a large extent sealed off from the ambient space surrounding the projection apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Patent ApplicationSerial No. PCT/EP2003/009427, filed Aug. 26, 2003, which published inGerman on Mar. 25, 2004 as WO 2004/025368, and is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The invention relates to a device for sealing a projection exposureapparatus with an illumination system, a reticle, a projection objectiveand an image plane, where the interstitial spaces between the individualelements of the apparatus are open to the ambient space.

BACKGROUND

A device of this type has been disclosed in EP 0 886 184, wherein avacuum-operated device is described which is arranged between a waferand an optical element. The device has an illumination field opening atits center, leaving a minimal upper gap to a lens surface and a furtherminimal gap to a wafer surface. The gas flow is introduced above andbelow the device and exits again within the device through slot-shapedopenings. As a result, contaminations, specifically dust grains, areremoved from the lens surface.

The task that has been set for the present invention is to provide adevice which can be arranged in the critical areas of the projectionapparatus but dues not absorb a large portion of, nor interfere with,the radiation that is present in those areas.

SUMMARY

According to the invention, the task is solved by arranging in at leastone of the interstitial spaces a gas purge device carrying a stream ofnitrogen or inert gas, where the gas purge device is of a shape and sizeso that one or more of the interstitial spaces are to a large extentsealed off from the ambient space surrounding the projection apparatus.

In a first inventive solution of the task, the space between aprojection objective and an image plane is sealed off to a high degreeby an appropriately dimensioned device to form a so-called containment,where the sealing effect occurs without contact. In lithographyprocesses at a wavelength of 157 nm, the radiation would be absorbed toa large extent in an air-filled space between the projection objectiveand the image plane, and it is therefore necessary to provide aprotective gas atmosphere using nitrogen or a noble gas. These gaseshave a low degree of absorption for the type of radiation used in thisapplication. Using pure nitrogen for the protective gas ensures that asubstrate coated with photosensitive materials receives the 157nm-wavelength radiation without loss and that the last surface of theprojection objective remains free of harmful substances.

In an advantageously developed embodiment of the invention, the gas-flowdevice is equipped with at least one gas-inflow device and at least onegas-outflow device, where the cross-sectional area of the inflow streamof nitrogen or noble gas can be larger than the cross-sectional area ofthe outflow stream. The at least one gas-inflow device can be configuredas a hollow orifice channel, and the gas outflow device can beconfigured in the form of seal gaps.

The not completely seal-tight containments are constantly replenishedwith gas through the hollow orifice passages, while the gas flows outagain through the seal gaps. The gaps have to have a large enoughoverlap and be dimensioned commensurately with the magnitude of theinflowing gas stream, so that no extraneous gas can enter by diffusionand no streams can flow in the reverse direction through the gaps. It isadvantageous if the interior space of the gas purge device is under aslight overpressure.

The inlet orifice channels used in the purge device should fill thespace in the containment as uniformly as possible and withoutturbulence. The throttle effect of the purge device should not occur inthe inlet orifice passage. Rather, it is advantageous if the gas leavesthe inlet orifice passage as a laminar stream. The sealing effectagainst the ambient space occurs as a result of the gas outflow beingchanneled through a sufficiently long gap passage.

According to a second solution in accordance with the invention, a gaspurge device can also be arranged in the space between the illuminationand the reticle. The seal gaps for the outflowing gas are in this caseformed by a stack of lamellar disks with ring gaps, in an arrangementwhere the lamellae can slide relative to each other.

The stack of lamellae is likewise designed as a seal against the ambientspace. The gas streams into the device through the inlet orificepassages and streams out through the lamellae that form the seal gaps.This arrangement has the advantage that the space to the side of thelight path remains largely free of installed elements so that it can beused for the positioning of the stage with the space remaining sealedwhen the reticle is moved in relation to the rest of the apparatus.

In a further embodiment of the invention, an arrangement of two largering-shaped plates that are laterally movable relative to each other maybe used for the seal, wherein one plate is fixedly connected to theprojection objective and the other plate is fixedly connected to the gaspurge device.

Only a very limited amount of clear space is available for the sealingarrangement between the reticle and the projection objective. It istherefore advantageous if the two plates are of a sufficient length sothat when the reticle is shifted to different positions, the two platesstill overlap each other to keep the gas-purged space sealed off.

Other features and advantages of the present invention will be apparentfrom the following detailed description when read in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES

The foregoing and other features of the present invention will be morereadily apparent from the following detailed description and drawingsfigures of illustrative embodiments of the invention in which:

FIG. 1 represents a principal outline of a projection apparatus for thefield of microlithography, which finds application for projectingcircuit structures onto wafers that are coated with photosensitivematerials;

FIG. 2 represents a lengthwise sectional view of a gas purge devicewhich is arranged between a projection objective and a wafer;

FIG. 3 represents a lengthwise sectional view of a gas purge devicewhich is arranged between an illumination device, a reticle and aprojection objective; and

FIG. 4 represents the apparatus shown in FIG. 3, wherein the reticle hasbeen moved sideways in relation to the illumination system and theprojection objective.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a projection apparatus 1 of a type that is known inprinciple from U.S. Pat. No. 5,638,223 and U.S. Pat. No. 6,252,712 whoseentire content is incorporated herein by reference. Therefore, thefunctional principle of an apparatus of this type is assumed to be knownand the following detailed description will be limited to those partsthat are relevant to the invention.

Systems of this type are used for the production of semiconductorcomponents and serve to project circuit structures onto a substrate thatis coated with photosensitive materials, consists in generalpredominantly of silicon, and is referred to as a wafer 2.

The projection apparatus 1 consists substantially of an illuminationdevice 3, a so-called reticle 5 which defines the structures that willsubsequently reside on the wafer, and an imaging system in the form of aprojection objective 7.

According to the basics of the functional principle, the structuresincorporated in the reticle 5 are projected onto the wafer 2 in areduced size.

After an exposure has been completed, the wafer 2 is moved in the x- andy-directions by means of positioning stages 26 which are fixedlyconnected to the overall apparatus 27, so that a multitude of individualfields can be exposed to the structure defined by the reticle 5. Atranslatory movement 25 of the wafer in the z-direction is likewiseavailable.

The illumination device 3 provides a projection light beam 4 as requiredto form an image of the reticle 5 on the wafer 2. The light beam isshaped in the illumination device 3 by means of optical elements in sucha way that when the projection light beam 4 falls on the reticle 5, ithas the specified properties in regard to diameter, polarization, shapeof the wave front, and other characteristics.

An image of the reticle 5 is produced with the light beam 4 andtransferred in a reduced size through the projection objective 7 to thewafer 2.

FIG. 2 illustrates a principal configuration of a gas purge device 8. Ina preferred arrangement, a ring-shaped inlet orifice channel 10 in thespace between the projection objective 7 and the wafer 2 provides alaminar inflow of the gas 23 into the cylindrical gas purge device 8.The orifice passage 10 can also be divided into segments along thecircumference, so that the inflow of gas can be controlled moreprecisely. The purging occurs in the purge area 13. As the radiationpassing through the purge area 13 needs to have a high energy level, thepurging with nitrogen or with an noble gas 23, helium in particular,serves to prevent the presence of certain radiation-absorbing gases,especially air, in the beam passage area 13.

There are two gaps located, respectively, at the top and bottom of thegas purge device 8, i.e., the gap 11 between the projection objectiveand the gas purge device, and the gap 11′ between the gas purge deviceand the waver. The gaps 11 and 11′ should be less than one millimeterwide. The pure nitrogen or noble gas 23 which is blown into the purgedevice streams out through the gaps 11 and 11′ into the ambient space orinto exhaust gas devices which may be part of the setup but are notshown in the drawing.

The passages through the gaps 11 and 11′ need to be long enough that noextraneous or ambient gas can enter into the device by diffusion.

The volume of gas 23 flowing in through the orifice passages 10 needs tobe larger than the volume flowing out through the gaps 11 and 11′. Thus,the cross-sectional area of the inflow passage can be slightly largerthan the cross-sectional area of the outflow passage in order to achievea desired ratio between the respective flow rates. As a result, there isa slight overpressure inside the gas purge device 8.

The tendency for a pocket of stagnant gas to form at the center of thering-shaped orifice 10 on the optical and mechanical centerline axis 19is prevented by slight asymmetries which are always present. Forexample, the gaps 11 and 11′ usually have different widths. It is alsopossible that one of the gaps, preferably the upper gap 11, is reducedto zero. In this case, the orifice channel 10 is in direct, seal-tightcontact with the projection objective 7 without leaving a microscopicgap, so that there is only the one gap 11′.

The gas purge device 8 is equipped with support bearings 18. Thebearings 18 are located on a bearing mount of a mechanism 27 which isnot illustrated in detail. The wafer 2 is likewise supported by thebearing mount 27. The bearings 18 are needed so that when the wafer 2 ismoved the gas purge device 8 can stay in place.

FIG. 3 shows a gas purge device 8′ enclosing the reticle 5. As in thearrangement of FIG. 2, the gas inflow occurs again through ring-shapedorifice passages 10. The gas 23 streams through the orifice passages 10into the interstitial space between the reticle 5 and the illuminationdevice 3 as well as into the interstitial space between the reticle 5and the projection objective 7. A stack of lamellar disks 14 is arrangedon the topside of the gas purge device 8′. The gas 23 flows out throughthe lamellae each of which forms a seal gap. The stack of lamellar disks14 consists of a plurality of lamellae 14′ arranged on top of each otherand configured as flat ring disks leaving an opening in the center so asto allow the radiation to fall on the reticle 5. The lamellae 14′ aremade of metallic materials that will hold up under the radiation. Thelamellae 14′ are held at a constant gap distance by balls and magnets 17which cooperate with soft iron inserts. The gas 23 in the gas purgedevice 8 can stream out through the stack 14 of lamellae, in particularthrough the gaps between the lamellae 14′ and through the gaps 20′.

The gas 23 streams inside the gas purge device 8′ from the space abovethe reticle 5 to the space below the reticle 5. The latter is seated atits outer ends through a three-point support 9 on an interior frame 24.The gas purge device 8′ is closed off at the bottom by a closure plate16. To provide a sufficiently wide gap 21 between the gas purge device8′ and the projection objective 7, an upper closure plate 15 of theprojection objective 7 is fixedly attached to the latter. Thisarrangement is chosen because only a very limited clearance height isavailable in this area.

The plates 15 and 16 are of ring-shaped configuration leavingsufficiently large openings through the middle of the plates 15 and 16for the light beam to pass through, taking into account that the plates15 and 16 can slide laterally in relation to each other. When thereticle 5 is pulled out to its extreme position relative to the overallapparatus, there still needs to be a sufficiently large overlap betweenthe two plates 15 and 16, i.e. half of the nominal gap passage length,so that no extraneous gas can ever enter and contaminate the purge area.

The interior frame 24 on which the reticle 5 is supported is movable onsliding stages 25 in the z-direction relative to the gas purge device8′, the stack 14 of lamellar disks, and the outer frame 28. Thearrangement is designed so that illumination is maintained when theinterior frame 24 with the reticle 5 is moved to different positions. Inorder to ensure the effectiveness of the seal in every position, thering gaps 20 which can have different diameters should always have aspecific ratio between width and passage length. The length of the gappassage to the width of the gap should always be in a ratio of 10 mm to20 mm length vs. 0.5 mm to 10 mm width. The gas purge device 8′ also hasring-shaped openings not shown in detail. By way of the gaps 20, thering-shaped openings and the stack 14 of laminar disks, the gas 23inside the purge device 8′ can flow out again.

The foregoing arrangement has the advantage that the space to the sideof the light path remains largely free of installed elements so that itcan be used for the measuring arrangement used in the positioning of thestage.

FIG. 4 shows the gas purge device 8′ moved sideways. As the reticle 5 ismoved on sliding stages 26 in the x- and y-directions in relation to theillumination system 3 and the projection objective 7, the stack 14 oflaminar disks shifts to a staggered position of the disks. The inflow ofgas occurs likewise by way of the ring-shaped hollow orifice channel 10.The nitrogen or the inert gas 23 streams out through the seal gapsbetween the lamellar disks 14′ and through the gaps 20, 20′, 20″, 21 andcan also be carried away from these locations by an exhaust gas devicewhich is not shown in the drawing.

A sideways shifting movement of the reticle 5 is required in order tosequentially expose a multitude of individual fields on the wafer 2 tothe projection of the structure defined by the reticle 5.

The removal of gases that would interfere with the exposure processshould occur within a few tenths of a second. The amount of gas need forthis purpose should be kept small.

While exemplary drawings and specific embodiments of the presentinvention have been described and illustrated, it is to be understoodthat the scope of the present invention is not to be limited to theparticular embodiments discussed. Thus, the embodiments shall beregarded as illustrative rather than restrictive, and it should beunderstood that variations may be made in those embodiments by workersskilled in the art without departing from the scope of the presentinvention as set forth in the claims that follow, and equivalentsthereof. In addition, the features of the different claims set forthbelow may be combined in various ways in further accordance with thepresent invention.

1-20. (canceled)
 21. A packer for use in a wellbore, comprising: a mandrel; a booster sleeve coaxially slidable along an outer surface of the mandrel and in sealing engagement with the mandrel; a first compression member coupled to the booster sleeve for selective axial movement therewith relative to the mandrel; a second compression member coupled to the booster sleeve for selective axial movement therewith relative to the mandrel; and a packing element disposed around the booster sleeve between the compression members.
 22. The packer of claim 21, wherein the first and second compression members are selectively limited in movement with respect to the mandrel.
 23. The packer of claim 22, wherein a first motion limiting member limits movement of the first compression member in a first direction relative to the mandrel and a second motion limiting member limits movement of the second compression member in a second direction relative to the mandrel.
 24. The method claim of 21, wherein respective motion limiting members couple the first and second compression members to the booster sleeve to restrict movement of the first and second compression members away from the sealing member.
 25. A method of sealing an annular area in a wellbore, comprising: providing a packer having a mandrel with a booster sleeve disposed around an outer surface thereof, first and second compression members coupled to the booster sleeve, and a packing element disposed between the first and second compression members; moving the first and second compression members together to expand the packing element in a radial direction by compressing the packing element; and applying a fluid pressure to the booster sleeve to move the booster sleeve axially relative to the mandrel, the first compression member moving with the booster sleeve as the second compression member is held stationary relative to the mandrel to further decrease the separation between the first and second compression members.
 26. The method of claim 25, wherein applying the fluid pressure is selected from applying the fluid pressure from above the packer to the booster sleeve and applying the fluid pressure from below the packer to the booster sleeve.
 27. The method claim of 25, further comprising restricting movement of the first and second compression members away from the packing element.
 28. A packer for use in a wellbore, comprising: a mandrel; a booster sleeve coaxially slidable along an outer surface of the mandrel; a first compression member coupled to the booster sleeve for axial movement therewith relative to the mandrel in a first direction, wherein movement in a second direction of the first compression member relative to the mandrel is limited and the booster sleeve is moveable relative to the mandrel in the second direction independent of the first compression member, the first direction being opposite the second direction; a second compression member coupled to the booster sleeve for movement therewith relative to the mandrel in the second direction, wherein movement in the first direction of the second compression member relative to the mandrel is limited and the booster sleeve is moveable relative to the mandrel in the first direction independent of the second compression member; and a packing element disposed around the booster sleeve between the compression members.
 29. The packer of claim 28, wherein the booster sleeve is in sealing engagement with the mandrel.
 30. The packer of claim 28, further comprising a first motion limiting device coupling the first compression member to the booster sleeve and a second motion limiting device coupling the second compression member to the booster sleeve, wherein the first and second motion limiting devices restrict movement of the first and second compression members away from the packing element.
 31. The packer of claim 28, further comprising a first motion limiting device coupling the first compression member to the mandrel and a second motion limiting device coupling the second compression member to the mandrel.
 32. The packer of claim 31, further comprising a third motion limiting device coupling the first compression member to the booster sleeve and a fourth motion limiting device coupling the second compression member to the booster sleeve, wherein the third and fourth motion limiting devices restrict movement of the first and second compression members away from the packing element.
 33. The packer of claim 28, wherein the first and second compression members and the booster sleeve are disposed between shoulders formed on the outer surface of the mandrel.
 34. The packer of claim 28, further comprising a first conical member coupled to the first compression member and a second conical member coupled to the second compression member.
 35. The packer of claim 34, further comprising a first slip member disposed adjacent the first conical member and a second slip member disposed adjacent the second conical member, each of the slip members having a gripping member extendable toward a surrounding surface for engagement therewith.
 36. The packer of claim 35, wherein relative movement between the slip members and the mandrel is restricted to only enable movement of the slip members toward the packing element.
 37. The packer of claim 36, wherein relative movement between the conical members and the compression members is restricted to only enable movement of the compression members toward the packing element.
 38. The packer of claim 34, wherein each of the gripping members are selectively connected to a respective one of the conical members using a shearable member.
 39. The packer of claim 38, wherein the shearable members are designed to disengaged at a predetermined force. 